PHOENIX — When the Celtics hired Brad Stevens, he was acutely aware that he was walking into a franchise steeped in tradition. Not only in terms of winning, but also in terms of winning with defense.

Under former Celtics head coach Doc Rivers, Boston consistently ranked among the NBA's best teams defensively in several statistical categories.

It was a perfect fit for Stevens, a wildly successful college coach whose teams at Butler won in large part because of their ability to defend.

Fast forward to this season where the Celtics' defense, much like the team's play, has been all over the map. Some nights they can lock opponents down with a strong, collective effort. Other times, it looks as though they just met and have no clue how to play, let alone play well as a unit.

And that has been part of the reason for this roller coaster of a season for the Celtics (19-35).

Boston is giving up 98.6 points per game this season which ranks 12th in the NBA. However, that number is up to 100.5 points per game since January which ranks 17th in the NBA and is a trend that Stevens is focused on steering the Celtics away from sooner rather than later.

There are several other defensive categories in which the Celtics are not among the league's top 10 which has been one of the many changes with this team this season.

"Right now, we've been in this little area where we're a top-14, top-15 defense in the league," Stevens said. "Can we become a little better over the course of the next two months?"

Boston's first crack at doing so will be tonight against a Phoenix Suns team that's coming off a 112-107 overtime win at Denver on Tuesday night.

Here are some other keys to tonight's game:

WHAT TO LOOK FOR: Prepare to see a lot of running on the part of the Suns as they look to continue to feast off a transition game that's averaging a league-best 18.4 fast-break points per game.

MATCHUP TO WATCH: Jeff Green vs. P.J. TuckerThis has been a rougher-than-expected season for Green who comes in shooting a career-worst 41.6 percent from the field, and just 38 percent since January. Meanwhile, Tucker is one of many young Suns players making the most of his opportunity to play consistent minutes. He's averaging a career-best 9.5 points per game and 6.4 rebounds which is also a career mark.

PLAYERS TO WATCH: Rajon Rondo has steadily improved his play since returning to action last month. We have seen this new-look Rondo unveil a better looking jumper that was on display during a 16-point, 6-for-7 shooting night against San Antonio last week. And we have seen him at times revert back to being the assist machine that he has been for so many years. Putting the two together on the same night with consistency, is the next hurdle for Rondo to clear.

STAT TO TRACK: The Suns are a three-point jacking squad like none other that's obvious in their NBA-leading 9.4 made threes per game. But unlike most teams that launch threes at will, Phoenix has made a concerted effort to not allow opponents the same let-it-fly status. The Suns defense is limiting opponents to 6.4 made threes on 19.3 attempts per game which rank No. 3 and No. 8 in the NBA, respectively.

A. Sherrod Blakely serves as Comcast SportsNet's NBA Insider. Read more from Sherrod here, or follow him on Twitter or Facebook.